For many years dental prostheses have been made for patients who have lost any number of their natural teeth. Prostheses of interest in the present invention are partial dentures, fixed temporary single unit temporary crowns as well as orthodontic appliances. Of prime interest to a patient needing artificial teeth is their appearance. The patient expects his or her dentist to be able to restore missing teeth with prostheses that both function comfortably for biting and chewing food and look esthetically pleasing. Dentists requiring such prostheses often employ the services of a dental laboratory, which is outfitted with the equipment and personnel required to build such prostheses, including computer aided design and manufacture equipment (CAD/CAM).
Since the patient's dental restoration will be visible to others, most dentists and patients are eager to have prostheses that look natural. If the prosthesis is for only one or two teeth and the patient has mostly natural teeth, a good match between the prosthesis and the natural dentition is very highly desirable.
Not only is the color match to the teeth and gums critically important, most patients do not want a metallic clasp attaching the prosthesis to their natural teeth to be visible. Even if the teeth of the prosthesis are well-matched, a metal clasp attaching it to the natural teeth indicates that they are false.
Dental prostheses are divided into two categories, fixed and removable. Fixed prostheses are tooth and/or implant supported prostheses that are bonded or cemented into place and are not routinely removed by the patient. The removable prostheses of concern in this patent application include partial dentures, bite or occlusal appliances, orthodontic appliances, snoring and sleep apnea appliances. Of prime interest in this patent application are temporary fixed single unit crowns and removable partial denture clasps.
Partial dentures are tooth, tissue and/or implant supported and is removable by the patient for routine cleaning and home care. The occlusal, orthodontic, snoring, mouth guard and sleep apnea appliances may be supported by tooth, implant, tissue or a combination thereof. The fixed single unit temporary crowns are cemented or bonded to place. They will be fixed to ether a prepared natural tooth or an implant abutment. They will remain in the mouth from a time period ranging from a few weeks to several months while the permanent crown is being made or while the patient's mouth is healing from surgery.
Temporary and provisional prostheses are sometimes made by the dentist but are generally fabricated by a dental laboratory. Partial dentures can have a metal substructure or be all acrylic and support a clasp. The non-metallic dental clasps that are the subject of this invention are also applicable and of use in orthodontia. Even though the detailed description describes clasps for partial dentures, it is understood that the description applies to orthodontic and other appliances as well.
In the past, dentists have had a variety of options when working with dental laboratories making prostheses for their patients. Esthetics, as well as cost, is of interest to all parties concerned. Until the present invention, dental lab customers often would choose between esthetics and cost.
An option that exists for fabricating dental clasps is a pre-formed clasp made of non-metallic material. These pre-formed clasps are bought pre-made from a company and then fitted to a particular prosthesis by hand. To get a pre-formed clasp in place, a channel is cut into the partial denture, and then the clasp is heated until it is pliable. At that time, the softened clasp is pushed into place on the partial denture by the dental technician.
In the past, as seen in U.S. Pat. No. 6,855,278 Lichkus et al discuss a process of making a dental prosthesis with a clear aesthetic clasp. The clasp of the '278 invention are not made of an acetal resin that is color-coordinated to the patient's tooth and gingiva as are the clasps of the instant invention.
The method claimed in '278 does not use the delivery method of this invention. Unlike the present invention, it requires the use of hot-press dental equipment. This adds to the cost, time needed to make the clasps, and the amount of material used to make the clasps.
Most dental laboratories do not use thermoplastic resins to fabricate clasps for dental prostheses. This is because until the present invention expensive hot-press equipment is needed, which is unavailable to most dental laboratories. The present invention uses a hand-held thermoplastic injection gun to make clasps out of thermoplastic resin without the need for expensive hot press equipment.
Acetal resin, the preferred material of use of this invention, is a highly crystalline thermoplastic, non-amorphous material. The material is an encapsulated polyoxymethylene copolymer of non-volatile cylindrical pellets. The characteristics of highly crystalline polymer include low to almost no water absorption and therefore no problems with bacteria and stain build up on acetal resin. The material will remain color stable for the life of the acetal resin. The low moisture absorption and chemical resistance of acetal resin allows it to be very resistant to deterioration over time. A preferred acetal resin of the present invention is sold as “Aesthetic Perfection” and is made and distributed by CDM, Inc. Albany, Oreg.
Besides avoiding the additional expense that has been mentioned, the current invention also takes significantly less time to form thermoplastic clasps than the hot-press equipment would take. Another positive feature of the dental clasp of the present invention is that less raw material used and less wasted, in making the clasps with the hand-held thermoplastic injection gun of this invention.